Conventionally, the following processes are known for producing an optically active 3-hydroxypropionic ester derivative.
1) A process for obtaining an optically active 2-substitued-3-hydroxypropionic acid by asymmetrically oxidating 2-substituted-1,3-propanediol by use of a microorganism (Chem. Lett., 1979, Vol. 11, 1379-1380).
2) A process for obtaining an optically active 3-hydroxypropionic ester derivative by reducing a 0.1% 2-formylacetate ester derivative by use of a microorganism belonging to the genus Candida, Rhodotorula, or Torulopsis (Japanese Patent Laid-Open No. 60-199389).
However, in the process 1), the diol compound used as a substrate is expensive and the stereoselectivity is low in the case where the 2-position has a substituent except for a methyl group. Furthermore, in the process 2), since a substrate in use negatively affects the reducing activity of a microorganism and an enzyme, the concentration of a starting material is extremely low. Both processes have significant problems as an industrial process.
On the other hand, for producing a 2-formylacetic ester derivative, the following processes are known.
3) A process for obtaining ethyl α-(formyl) 2-methyl-1,3-dioxolane-2-propionate by formylating ethyl 2-methyl-1,3-dioxolane-2-propionate with NaH and ethyl formate, followed by subjecting to distillation purification (Phosphorus and Sulfur, 1986, Vol. 28, 330-345).
4) A process for obtaining crude ethyl 2-formylphenylpropionate by formylating ethyl phenylpropionate with a sodium metal and ethyl formate (Eur. J. Med. Chem., 1988 Vol. 23, 53-62).
However, in any one of the processes, a reaction product contains an unreacted starting material and a large amount of impurities such as a mineral oil derived from NaH. Therefore, for obtaining a highly purified product, a purification step using distillation, crystallization or column is required. There are problems mentioned above for putting such a process to an industrial use.